Serving for registering process variables in automation technology are sensors, which have at least one sensor element and which are installed, for example, in fill level measuring devices, flow measuring devices, pressure and temperature measuring devices, analytical measuring devices, etc. The devices register the corresponding process variables, fill level, flow, pressure, temperature, and analytical data, such as pH-value, turbidity or conductivity. Serving for influencing process variables are actuators, such as, for example, valves or pumps, via which the flow of a liquid in a section of pipeline or the fill level in a container can be changed. Sensors and actuators are generally referred to as field devices. Referred to as field devices in connection with the present disclosure are, however, all devices that are applied near to the process and which deliver, or process, process relevant information. Field devices are usually composed of a plurality of components, whose structure and construction are as simple as possible, in order to keep the manufacturing effort using conventional manufacturing methods as small as possible.
A sensor element of a field device of automation technology includes usually at least one sensitive component, via which an electrical signal is converted into a process variable of the medium to be determined or monitored or a process variable of the medium to be determined or monitored is converted into an electrical signal. The sensitive components fulfill respectively defined functions. In addition to the sensitive components, purely mechanical components can be present. Consider, for example, a vibronic sensor for limit level, density, and/or viscosity determination. In the case of a vibronic sensor, a single rod or an oscillatory fork oscillates at a predetermined resonant frequency. In the case of an electrical resistance element, for example, a length of platinum wire, applied for temperature measurement, it should have a defined resistance value at a predetermined temperature.
Usually, the adjusting of the oscillatory fork to the resonant frequency or the tuning of a resistor to a defined resistance value occurs via a trimming-process. During trimming, sufficient material is removed, or added, that the oscillatory fork oscillates with the predetermined resonant frequency, or the resistor has at a certain temperature a predetermined resistance value.
The trimming is a relatively complex process. Depending on sensor element, or depending on component of the sensor element, too strong trimming can destroy the item. Also, removal of material negatively influences the long term stability of the component or the sensor element.
An object of the present disclosure is to provide a method for targeted manufacturing of a sensor element or for targeted manufacturing of a component of a sensor element.